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Old December 3rd 18, 01:53 AM posted to rec.photo.digital
Neil[_9_]
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Posts: 521
Default Just What is a Bitmap?

On 12/2/2018 5:17 PM, Carlos E.R. wrote:
On 02/12/2018 17.03, Neil wrote:
On 12/2/2018 7:49 AM, Carlos E.R. wrote:
On 01/12/2018 23.45, Neil wrote:
JPEG is a file format that contains a version of the original bitmap
image and organizes aspects of the image such as its resolution relative
to the original, file size and other factors. One original purpose of
the jpeg format was to allow journalist photographers to send images
across the internet when 300bps modems were commonplace.

I'm unsure a jpeg can be considered a format usable for bitmap
manipulation, because it is a lossy format. So someone creating or
changing a bitmap would not use jpeg because individual pixels can
change or just be lost. A bunch of spatially contiguous pixels can be
grouped and get the same value - when in the original they were
different.

That is a different issue. There are several lossy bitmap formats, one
of which is jpeg. Sometimes its lossy aspect matters, sometimes not.


If you are going to do bitmaps, and expect the pixels to stay the
*exact* same the next time you open the file, don't use a lossy format,
because it can change your pixels...

Why are you under the impression that I disagree that jpeg is lossy, or
is it that you think that's *always* the most important aspect of an
image? Just curious.

--
best regards,

Neil